I read the article about Plaxo service. How do they have the plan to
make money?  It is having to do with PKI identity authentication?  It
must be detail and make sense to be satisfactory answer.

Good questions; in reverse order:

PKI might be involved: http://www.plaxo.com/about/careers

Plaxo is looking for an experienced systems engineer with experience
building extremely large-scale Internet-based security backends to
lead the design and development of our new service. You will have deep
proficiency and experience in a variety of security technologies (PKI,
S-MIME, CA, Open SSL, etc.) ...


As for the first part:

http://zdnet.com.com/2100-1106-965351.html

Parker's company is backed in large part by a $2 million round of
venture funding last February, led by Sequoia Capital. The product
will go live Tuesday and will be distributed freely. He declined to
discuss the company's potential plans to generate revenue, but did say
Plaxo would not sell or otherwise use any member's contact information
without permission.


http://www.wired.com/news/technology/0,1282,56322,00.html

When asked exactly how the company intends to generate revenue, the
decidedly secretive founder would confirm only that Plaxo is not meant
to be spyware or adware.

"We think one of the most clever aspects of what we're doing is the
business model, but right now we're talking exclusively about the
product launch, not about the business model," Parker said.

Doc Searls, a senior editor at Linux Journal, was not convinced. 

"If they won't explain how they intend to make money, one can only
assume they intend to spend it," Searls said. "The product looks like
a new way to hire a company to annoy your friends. It feels like spam.
It's annoying, and I don't think there's a viable plan here."


This last article talks a bit more on the whole profit issue.


http://www.redherring.com/vc/2002/09/bubbleboys0923024529.html has:

This clandestine startup is Plaxo, and its founder is Sean Parker, the
22-year-old last seen helping Shawn Fanning build Napster. His new
project is a consumer-oriented application to manage contact
information in Microsoft Outlook.

He doesn't expect short-term revenue; first, Plaxo will hook consumers
on the gratis software, then the firm will sell it to corporations.

Yes I already read this article. What is exact way for Plaxo to make
money? How do this company make money in the PKI or digital
identity??? How do anybody make money in consumer
identificcation/authetnication? But the question is specify about
Plaxo.Do they want to be $billion company? Mike Moritz is clever man.
Why do he invest here??

It does not appear (at least to me) that PKI is a
critical part of Plaxo's business plan (other than
it being essential to their base product's security
issues...) at all.

The value of Plaxo to businesses by Plaxo organizing
and keeping all their contact lists (which would include
customer lists) up to date, by itself, could be worth
quite a bit.  Someone moves, and they (through Plaxo)
having the ability to not go to the post office, etc. but
to update all of their address (physical and email, etc.)
information in one click (at no charge) might be very
appealing.  I know that (currently!) Plaxo does not appear
to do that, but it wouldn't be surprising if they (in the
future) would ask people if they would like the ability to
have their personal information updated for their magazine
subscriptions, their driver's license, their phone service,
etc. in one click.

The software has the potential to be sold to companies
who want to use it both in-house for their employees,
but also through their websites ala Plaxo to keep their
cutsomer database updated.

Also, if they were to become popular, Plaxo could segue
their service into other areas of the Outlook universe,
such as database synchronization or system backup services,
etc.

As for investors (not being specific here...) being smart,
there has been lots of money invested (some large amounts
by very smart people as well) in products that might have
seemed like a good idea at the time, but didn't pan out.